Telecommunications cables are often located in underground ducts that are accessible at ground level at access points along the length of the duct. Redundant cables can be jammed in the ducts either by becoming adhered to the duct or by having subsequently installed cable twisted around them. Until now, removal of the cables has been facilitated by application of a tensile force to the cable, which might, in some cases, free a jammed cable and allow its extraction. However, if the cable cannot be easily extracted in this way, applying tensile force can damage the duct and/or the other cables within the duct, resulting in costly and time-consuming repair work or even discarding of the damaged cables and/or duct. Removal of redundant cables reclaims valuable duct space that can then be used to install new cables. The high cost of installing new ducts can be delayed if optimal use is made of the duct space.
It is an object of the present invention to alleviate these problems in a simple and effective manner. The invention is as stated in the appended claims. An advantage of using a path-finding element is that jammed cables can be eased and separated away from other cables or from the duct without damaging the other cables or the duct itself. An additional advantage is that there is significantly less risk of breaking the redundant cable. The path-finding element or head is remotely operable such that it may be controlled from outside the duct to negotiate the obstructions it encounters inside the duct. Longer lengths of duct are accessible than would be without the head. The path-finding head may be detachable so that a head may be removed and changed, such that the appropriate head for the particular job concerned can be attached. The head may be outwardly deformable, so as to expand and gently push cables or other obstructions out of the way without damaging them. The head may include a seal activated by pressurisation of the sub-duct. The seal enables the trapping of gas inside the head so as to facilitate the expansion of the deformable head.
The head may include a cutting portion at its front end, allowing the head to cut through an obstruction or enable the release of a cable that has become adhered to the duct.
The cutter may be a chisel head cutter for chiselling through small gaps between cables or between the cable and the duct, allowing gentle cutting or displacement of the obstruction.
The cutter may be a rotational cutter for cutting through obstructions where required. The rotational cutter is activated by relative movement of the sub-duct and the cutter. A helical thread translates linear movement of the sub-duct to rotational movement of the cutter. In this manner a rotational cutting action may be achieved simply and effectively by a reciprocating motion of the sub-duct.